What would be great would be the ability to test for disease in a way where there’s no or low pain (not invasive) and lots of gain (actionable data about the disease process itself, its progression and the success of treatment).

That’s where biomarkers come in.

Just about anything produced by the body could be a biomarker—an indicator of a normal or abnormal disease process—as long as it’s measurable and changes in relationship to disease—for example, going up if the disease gets worse and down if it responds to treatment.

The concept of the biomarker isn’t exactly new. What is cholesterol, after all, if not a biomarker for cardiovascular disease? And blood sugar, if not a marker for diabetes?

Some biomarkers have proven more successful than others. Prostate-specific antigen and CA-125 are proteins detectable in blood that have long been used as biomarkers for prostate and ovarian cancer, respectively, but their effectivenessis under a lot of scrutiny.